Role of Receptors in the Metanephric Mesenchyme

描述（由申请人提供）：先天性肾脏疾病是儿童慢性肾脏疾病的主要原因。该应用程序的广泛的长期目标是了解肾脏发育的分子控制，以影响先天性肾脏疾病。成纤维细胞生长因子受体（Fgfrs）通过衔接蛋白（如成纤维细胞生长因子受体底物2（Frs 2））发出信号，对肾脏发育至关重要;然而，由于突变胚胎的早期致死性，全球小鼠基因靶向尚未揭示Fgfr或Frs 2信号在胎儿肾脏中的全面影响。此外，有条件删除 Fgfr 1和Fgfr 2在后肾间充质（MM）中具有Pax 3cre线导致肾发育不良。为了阐明Fgfr/Frs 2？信号传导在肾脏发育后期MM中的作用，用1. Fgfr 1在MM发展的日益受限和后期阶段的缺失; 2. Fgfr 2中Frs 2？结合位点的全局点突变。在早期MM中具有Fgfr 1缺失的突变小鼠具有Pax 3cre系和Fgfr 2中Frs 2 <$结合位点的点突变。在PFLR小鼠中，避免了Fgfr 1和Fgfr 2的Pax 3cre缺失所观察到的肾发育不良;然而，PFLR小鼠在输尿管和肾单位谱系中出现了输尿管芽（UB）分支缺陷、过早的肾单位祖细胞（NP）耗竭和进行性囊肿形成（显示Fgfr 2下游的Frs 2介导的信号传导的重要性）。PFLR小鼠中的输尿管缺陷始于扩张和过度增殖的UB尖端，其似乎与不适当的Ret信号传导有关。这些小鼠似乎还具有纤毛结构、典型Wnt信号传导和平面细胞极性（PCP）的缺陷，每一种都可能导致发育和囊性缺陷。用Six 2cre系（“SFLR”）产生的另一组小鼠，其Fgfr 1的缺失略晚于PFLR并且仅在NP中（比PLFR更受限制）引起NP耗竭和来自肾单位谱系的囊肿，但没有明显的输尿管缺陷。SFLR NPs最初正常形成，但似乎失去干细胞样标记物并发生凋亡。用晚于SFLR在肾囊泡中缺失的Wnt 4cre系（“WFLR”）产生的第三组小鼠没有明显的肾异常。该假说认为，通过后肾间充质中的Frs 2？对FGFR信号传导的空间和时间调节对于发育期间的输尿管和肾源性谱系模式至关重要。为了检验假设，生成了以下目标：目标1。描述突变小鼠等位基因系列中非自主输尿管和自主肾发生谱系模式缺陷。将评估胚胎和出生后肾脏的结构和功能缺陷。目标二。确定肾间质中Fgfr/Frs 2 <$信号传导导致输尿管形态发生缺陷和膀胱发生的机制。将评估Bmp 4/Ret/Erk轴和纤毛、典型Wnt和PCP缺陷的作用。目的3：确定肾间质中Fgfr/Frs 2？信号传导导致肾单位祖细胞过早耗竭的机制。将在NP细胞培养物中评估通过无偏测定鉴定的Fgfr/Frs 2？信号传导的候选靶标。

DESCRIPTION (provided by applicant): Congenital kidney diseases are leading causes of chronic kidney disease in children. The application's broad long-term objectives are to understand molecular control of kidney development to make an impact on congenital kidney disease. Fibroblast growth factor receptors (Fgfrs) that signal through adapter proteins such as fibroblast growth factor receptor substrate 2¿ (Frs2¿) are critical for kidney development; however, global mouse gene targeting has not revealed the full impact of Fgfr or Frs2¿ signaling in fetal kidneys due to early lethality of the mutant embryos. Furthermore, conditional deletion of Fgfr1 and Fgfr2 in the metanephric mesenchyme (MM) with a Pax3cre line led to renal dysgenesis. To elucidate roles of Fgfr/Frs2¿ signaling in the MM at later stages of renal development, compound mutants were generated with 1. Deletion of Fgfr1 in increasingly restricted and later stages of MM development and 2. Global point mutations in the Frs2¿ binding site in Fgfr2. The mutant mice with Fgfr1 deletion in early MM with the Pax3cre line and point mutations in the Frs2¿ binding site in Fgfr2 (PFLR mice), escape the renal dysgenesis seen with Pax3cre deletion of Fgfr1 and Fgfr2; however, PFLR mice developed ureteric bud (UB) branching defects, premature nephron progenitor (NP) depletion, and progressive cystogenesis in both ureteric and nephron lineages (showing importance of Frs2¿ directed signaling downstream of Fgfr2). The ureteric defects in PFLR mice start with dilated and hyper- proliferative UB tips that appear to be linked to inappropriate Ret signaling. The mice also appear to have defects in ciliary structure, canonical Wnt signaling, and planar cell polarity (PCP) that each may contribute to the developmental and cystic defects. Another set of mice, generated with a Six2cre line ("SFLR") that deletes Fgfr1 slightly later than PFLR and only in NPs (more restricted than PLFR) cause NP depletion and cysts from the nephron lineages, but have no apparent ureteric defects. SFLR NPs initially form normally, but appear to lose stem cell-like markers and undergo apoptosis. The third set of mice, generated with a Wnt4cre line ("WFLR") that delete in renal vesicles later than SFLR have no apparent renal abnormalities. The hypothesis is that spatial and temporal regulation of Fgfr signaling through Frs2¿ in the metanephric mesenchyme is critical for both ureteric and nephrogenic lineage patterning during development. To test the hypothesis, the following Aims were generated: Aim 1. To characterize the non-autonomous ureteric and autonomous nephrogenic lineage patterning defects in the allelic series of mutant mice. Embryonic and post-natal kidneys will be assessed for structural and functional defects. Aim 2. To determine mechanisms by which Fgfr/Frs2¿ signaling in kidney mesenchyme leads to ureteric morphogenesis defects and cystogenesis. Roles of the Bmp4/Ret/Erk axis and ciliary, canonical Wnt and PCP defects will be assessed. Aim 3: To determine mechanisms by which Fgfr/Frs2¿ signaling in kidney mesenchyme leads to premature nephron progenitor depletion. Candidate targets of Fgfr/Frs2¿ signaling identified by unbiased assays will assessed in NP cell cultures.